Parts of the country have been inundated since Friday, prompting disaster authorities to warn of floods in multiple rivers.

"So far, 42 people have died in rain-triggered disasters and five are missing," Shanti Mahat, spokeswoman for Nepal's National Disaster Risk Reduction and Management Authority, told AFP.

At least 37 were killed by landslides in the eastern district of Illam.

"Heavy rains overnight caused the landslides," said local district official Sunita Nepal.

"With roads blocked, some areas are difficult to reach. Rescue workers are heading there on foot."

Rivers in the capital Kathmandu also swelled, inundating settlements along their banks.

Security personnel were deployed to assist rescue efforts with helicopters and motorboats.

Landslides have blocked several highways and disrupted flights, leaving hundreds of travellers -- many returning after celebrating the Hindu festival of Dashain -- stranded.

Monsoon rains, usually from June to September, bring widespread death and destruction every year across South Asia, but the numbers of fatal floods and landslides have increased in recent years.

Experts say climate change has worsened their schedule, frequency and intensity.